Modulator arrangement



- Patented Jan. 6, I UNITED STATES.

PATENT OFFICE I 2,268,837 MODULATOR menswear Werner Lutzenberger, Berlin-Eichkamp, Germany, asslgnor 'to Fides Gesellschaft fiir die Vcrwaltung und Verwertung vongewerblichen Scliutzrechten m. b. 11., Berlin, Germany, a corporation of Germany Application May 20, 1939, Serial No. 214,696

. I In Germany May 21, i938 iciaim. (01. 179-1715) The invention relates to modulatpr .arrangements and demodulator arrangements with nonlinear resistors, more especially with dry-contact rectifiers or diodes such as employed in the carrier current field and measurements to move a frequency'or a frequency band into another position in the frequency spectrum. The frequency or th frequency band to be converted lS apphed hereby to the-modulator and more especially across a filter arrangement, and the non-linear resistor or resistors are controlled by a carrier frequency providing the desired frequency displacement. The converted signal vmay then be derived at the output terminals.

Often it is desired to have solely the converted frequency in the output of the arrangement whereby at least the signal frequency and the carrier frequency are suppressed. To suppress one ofthese frequencies as well as other undesirable modulation products in the modulator output, circuit arrangements have become known which were 'obtained,by connecting two nonlinear circuits; On these so-called push-pull modulators it is often necessary to employcompensation methods to suppress the, signal fre-' quency or the carrier frequency still appear-- ing in the'output, more especially in the casewhere thecarrier frequency employed is relatively low. It is known to this end to apply the signal frequency and'the carrier frequency respectively in suitable phaseand amplitude to the output of the modulation arrangement. But this is a cumbersome method and requires con.- siderable means as well as an additional consumption-of power.

. The conditions are much more favorable when using the known double push-pull arrangements. more especially an arrangement as has obtained a decoupling of all terminal pairs.

quency as well as other undesirable modulation products. It is for these reasons and for other advantages that the-ring modulator is now generally in use.

However, there is still a disadvantage inherent to ring modulator arrangements and to all dou-' ble push-pull arrangements, namely, that. it is necessary to utilize possibly four non-linear resistorsallhavingthe same characteristic so as "to completely suppress in the output the carrier frequency and the signal frequency. -It is possible to avoid the necessity of having completely non-linear resistors in that in accordance with other known proposals the resistors are chosen in resistor I.

, linear resistors.

in this case the requirements in usabledry contact rectiflers in a production series is rather low so that it is often necessary to resort to compensation methods for suppressing a residual potential of the carrier frequency and/or of the signal frequency still existing in the output. Hence, an arrangement would be much more favorable which with a smaller number of nonlinear resistors would already assure a suppression of the carrier frequency and signal push-pull modulators are, however, not suited to this end since, as already stated, only one of the two frequencies is thereby suppressed in the modulator output.

In describing my-invention reference will be made to the attached drawing wherein Figures 1a, 1b and, 1c inclusive are basic diagrams used to illustrate my invention while Figures 2, 3a, 3b and 4 illustrate schematically four .difierent embodiments of my novel. modulator in which thevoltage modulated andmodulating voltages are suppressed in the output. I v

In accordance with the invention the modulator'arrangement is designed as a bridge circuit such that the one-half of the branches-of the bridge is formed by non-linear resistors while the other half is formed by linear resistors,

mor especially by ohmic resistors. Bridge cir-.

cuits are" meant hereby to be the' actual bridge circuits accordingto Figure 1a, as well as the equivalents thereof. Thus, Figure 1b shows a a differential bridge. arrangement and Figure 1c shows abridged T-circuit. The non-linear resistcrs are designated by l in the Figures la to lo and the linear resistors are designated by 2, or vice versa. In the bridged T-circuit, according to Figure 10 by meansof which the present invention will be elucidated, there is placed in a series branch a differential transformer winding DT and between the transformer winding center and the other series branch a further resistor 2 inductively coupled therewith. One of the resistors is formed by one or several non-linear resistors which can be controlled between a maximum value and minimum value and the other resistor is formed by one orseveral As non-linear resistors dry, contact rectiflers or diodes are chosen in particular. with the modulator constructed in accordance with the present invention, a modulation arrangement is realized having onlyqnehalf of the non-linear resistors as compared with the push-pull and double push-pull arrangements required for the same results as regards the suppression of the carrier frequency and signal frequency in the modulator output. The

resistance value of the constant resistance is chosen hereby between the two limit values of accordance with certainother laws.- But also the controllable non-linear resistance, and more The differential transformer has a.'

lator arrangement consists of the, differential transformer T, the resistance 2 placed in the parallel branch and the inductively coupled resistance v I 2 It is assumed that Ri=Rz=R. The output current I: of the modulator arrangement is then established by the equation:

- Now if one of theresistances, such. as for instance the resistance varies periodically between the highest resistance value a E 2 and the lowest resistance value andif the resistance value of the other resistor is constant and lies between these two limit resistance values and chosen more especially to-be:

the output current 'changes its polarity periodically. There follows under the assumption that R=W1=vfi that:

440s JFS+Wz For'the lowest resistance value of there is:

I2 E 1E r/D E 451-1;

.for

S M f2? For the highest resistance value '2 "i there is accordingly? i i i- =.Ji. will 4 'D S yawn a/Es 4H+1 The equations show that the arrangement epfrequency does not ap pear in the output if the equation R=W1=VDS is fulfilled. An advantageexists however if the resistor m 2 is variable whereby its value which can only be calculated approximately can be so adjusted that the signal frequency disappears entirely in the output; Just as in the case of constituting the resistor 5 by a non-linear resistance which varies periodically between a maximum value and a minimum v value, also the resistor 1 can be formed by a non-linear resistance and by a constant resistance whose value is to be chosen in accordance with the points outlined in connection with For controlling the non-linear resistance formed, for instance, by a dry contact rectifier or by a diode, a carrier frequency of preferably rectangular pattern is utilized-in accordance with the desired displacement of 'the signal. When 3 employing but one non-linear resistance element this arrangement is'however not yet sufficient to suppress the carrier frequency in the output without using aspecial compensation circuit.

- The arrangement behaves just as a. push-pull modulator arrangement but requires only onehalf of the non-linear resistance elements.

' In the example of construction, according to Figure 3a, an arrangement is shown in which the non-linear resistance is formed by two dry contact rectifiers or diodes connected in pushpull. The carrier. frequency source 0 is placed between the connection point of the two resistance elements and the centers of two inductances or resistances P arranged on both sides of the arrangement, or according to the example of modulator on account of the use of the differential transformer and of the resistor so coupled inductively therewith, has the advantage over the push-pull modulator that as regards the suppression of the carrier frequency and signal frequency in the output, it behaves in thesame manner as a double push-pull modulator. The

circuit can be simplified if, according to the example shown in Figure 4, the resistor is a controllable non-linear resistor, more especially if it is formed of two dry contact rectiv flers or diodesplaced invpush-pull. The carrier jerates as-periodic polarity changer. v, The signal 7 elements and thecenter of the transformer winding. Therefore, in this case only a single transformer is required.

The arrangement according to the invention which could be termed suitably a bridge modulater to distinguish it from the known arrangements requires, as already pointed out, only one half of the non-linear resistors as compared with theknown modulators for the same results in regard to the decoupling of the modulator output from the signal frequency terminals and carrier frequency terminals. The examples of construction, according to Figures 2 and 3, have the further advantage over the ring 'modulatorin that they can be easily constructed also when employing tubes. A .double.push-pull modulator utilizing tubes requires, however, as is known, a

considerable number of means. Moreover, the

tubes employed can be united in a single vessel. Also duo-diodes may be employed in a manner known as such.

The damping during-operatiomof the bridge modulator according to the invention is the'saine as that of the ordinary push-pull modulator as can be proven by calculation, As compared with the push-pull modulator, the further advantage exists that in the bridge modulator the variations of the input signal current 11 are substantially smaller such as can be seen from the following.

The input current (Figure 2) is:

W1Ws+ r i' 1( 1+ +WI(RI 2) and if Ri=Rz= R; v

in while I1 varies in case of the tion according to What is claimed is: In a system for intermodulating two alternating voltages of different frequencies to obtain voltages-0f other frequencies related to the frequencies of said two voltages and substantially push-pull connecsuppressing voltages of the frequency of the frequencies of the two original voltages, a two-wireline having input terminals and output terminals connected with a load impedance, a transformerhaving a hut winding and having aidiiferential secondary winding connected in series with'one wife of said line, a resistance coupled in shunt to said first winding, a non-linear controllable resistance variable between tvirovalues connecting 1 a point between the windings of said diflerential secondary winding to the other side of said line,

saidiirst resistance having a'value intermediate the limitsv of'variation of said controllable resista'nce, means for im one of said voltages on the input terminals of said line and means for varying the value-of said'controllable resistance voltages v WERNER LU'IZENBERGER.

in accordance with the other of said I 

